tons) less than when at home. Though in healthy people it may be difficult to detect many changes arising from these causes, we may see that they really are very powerful. Phthisical patients, after a short residence here, improve (the pathological changes fade out), and often they become robust. A lessened atmospheric pressure is also very beneficial in many acute diseases, and especially in those of the lungs. The fierce New Zealand gales pump air into rooms at high pressures, and thus increase disease and retard recovery. Diminution of atmospheric pressure, too, causes a change in the shape and size of the various organs—e.g., the Aymaras, who inhabit the Andean heights, have long deep chests, with large lungs and short legs; these and other peculiarities of structure in them are directly due to lowered atmospheric pressure. People who climb lofty mountains soon experience great fatigue because their legs feel so heavy. When walking, our limbs swing freely like pendulums, and feel of little or no weight because of the peculiar formation of the hip, knee, and ankle-joints. If all the muscles and ligaments were cut through which attach the thigh to the trunk it would not fall off, because the atmosphere presses the head of the femur against the acetabulum. This pressure is 25 pounds. In like manner the leg is attached to the thigh by a large joint, the pressure on which is 60 pounds; so with the ankle joint —thus the weight of each limb, both upper and lower, is much lessened. As in ascending a height, so in any case where the pressure is lessened, the weight of the limbs will increase, and therefore fatigue would a little earlier set in during a long walk in New Zealand than in England. Yet other altered climatic conditions affect the immigrant. Though the amount of heat received by each hemisphere is exactly equal, yet is its distribution unequal; for, owing to the earth's position, the southern summer is nearly eight days shorter than the northern, and its winter so much longer (Somerville). The solar rays fall more directly on the southern hemisphere, and their heating power is consequently greater by one-eighteenth of their whole intensity; but as solar rays are composed of heat, light, and actinic rays, all three act more directly and more intensely in the southern hemisphere. As each of these varieties powerfully affects all organic and inorganic substances, therefore variations in the amount or intensity, or distribution of all combined, or of each one singly, affects the immigrant both directly and indirectly. In vegetation is easily seen the effect of sunlight—for vegetation grown in the dark is pale, and often sickly. Moreover, Sachs, a German botanist, has shown that, in the sunlight, starch grains travel in ten or fifteen minutes from the stems of plants to the chlorophyll grains in the leaves, and that these and many other changes would not occur if the light and actinic rays were absent. He also shows